Conversation

They're public rooms and not only can anyone join but anyone can view without joining. Matrix E2EE doesn't scale to a room with thousands of members and it would essentially brick them to enable it. It wouldn't provide privacy and would lose features like server-based search.
1
5
Also note that Matrix E2EE only encrypts message content. It doesn't encrypt any of the metadata for messages such as the time it was sent and who sent it or even emoji reactions to messages. It also doesn't encrypt state events like join, leave, kick, ban and the rest of them.
1
7
You can see how much it doesn't encrypt by making a new session and looking at your private rooms without cross-verifying your new session to get the keys synced to it. You can see everyone in the room, all the messages and state events, etc. You just can't see message content.
2
6
There are large public rooms with E2EE encrypted because they're sharing illegal content and want to make it substantially more difficult for servers to moderate it or handle takedown requests. It's mainly a way of certain sketchy servers to try to disown responsibility for it.
1
8